The embodiments herein relate generally to the blending of natural gas liquids into hydrocarbons and, more particularly, to a method of blending natural gas liquids into liquid hydrocarbons, such as gasoline, using a series of pressurized tanks with internal mixer-eductors.
Natural gas liquids (NGLs) either extracted from natural gas or crude oil, or as a product or byproduct of refining, chemical processing, or biochemical processing may be blended into liquid hydrocarbons for a variety of reasons. For example, butane may be blended into gasoline to increase the value of the butane, to increase the supply of gasoline, and to meet area specific and seasonal specific volatility limits.
Conventional methods for blending NGLs, such as butane, into natural gasoline, motor gasoline, condensate, crude oil, or the like include in-pipe or in-tank blend options only. In-pipe blending does not provide a method of good mixing, resulting in unstable and inconstant volatility measurements. In-tank blending requires long time delays in sampling and measurement and poses risks due to incomplete blending and the use of non-pressurized tanks. Thus, conventional methods do not include a mixer and also do not continuously analyze downstream of the mix point, rather, completion of analysis of conventional methods are a spot analysis in nature, and are delayed in reporting, often following delivery of product to the downstream equipment. The gasoline or crude product quality is inconsistent and, as a result, a significant amount of NGL upgrade value to gasoline or crude product is lost due to the need to maintain a conservative margin of error. Incorrect blending, particularly on the high side, can result in large financial or civil penalties for the blender.
Because the existing systems release hydrocarbon product upon blending and sampling but prior to receiving results of sampling, the chance of off-specification products is increased. To mitigate the risk of off-specification products, the existing systems reduce the amount of NGLs that are blended, thereby being inefficient.
In other words, existing systems do not retain blended product and certify the effectiveness of the blend. Moreover, existing systems are less effective in maximizing blending to reduce chances of off-specification production.
Therefore, what is needed is a blending system and method that provides a more consistent sample to analyze, eliminates stratification and bad mixing, and allows for continuous and accurate monitoring of the gasoline or crude product.